Synthesis of functionalized hydrazonoyl chlorides through an unexpected Sc(OTf)3-catalyzed Friedel–Crafts reaction

Abstract

A variety of complex functionalized hydrazonoyl chlorides were prepared in good yields through a Sc(OTf)₃-catalyzed Friedel–Crafts reaction of easily available arylhydrazonoyl chlorides with cyclobutanes under mild reaction conditions. The reaction showed a broad substrate scope and good functional group tolerance for various hydrazonoyl chlorides. More importantly, the obtained complex functionalized hydrazonoyl chlorides easily underwent (3 + 2) and (3 + 3) cycloadditions to afford various N-heterocycles in good yields. The present method features gram-scale preparation, high regioselectivity, the preparation of novel, complex functionalized hydrazonoyl chlorides, and Friedel–Crafts-type ring-opening reactions of cyclobutanes.